1 Advisor: Mr President! Something curious is happening over at the Large Hadron Collider in Switzerland.
1 Allosaurus: RAAARRRHH!!
2 Advisor: Yes, sir, and France.
2 Allosaurus: RAAARRRHH!! RAAARRRHH!! RAAARRRHH!!
3 Advisor: I've never known a President to have such a good grasp of scientific issues before.
3 Advisor: Or of where Switzerland is...
4 Allosaurus: Raaarrrhh!?
4 Advisor: And yes, it is a new tie, sir. Thank you for noticing.

Although the Large Hadron Collider experimental headquarters is in Switzerland, the collider itself is nearly 9 kilometres in diameter and extends underground into France. In fact, most of the collider ring is under French soil.

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2020-09-20 Rerun commentary: This handy user-created Google Maps overlay shows where the Large Hadron Collider is, relative to surface features.

And just in case the link dies, here's a copy of the map (click for a huge version):

In this map, CERN facilities are shown as coloured blocks outlined in black. CERN headquarters is the large blue block at the bottom of the map. There are subsidiary access points and experiment sites located at various points around the ring. The main facilities not on the LHC ring are on the smaller Super Proton Synchrotron collider ring.

The LHC ring extends directly under the French towns of Saint-Genis-Pouilly, Crozet, Versonnex, and Ferney-Voltaire, and the Swiss town of Meyrin (between CERN HQ and Geneva Airport; the northern part of Meyrin is labelled "VIOLET" on the map).

If you switch the interactive version to aerial view and zoom in, you can see exactly which houses in these towns the LHC passes under. It also goes directly under at least three schools that I can see. Imagine secretly exploring the basement tunnels under your school with your D&D buddies and finding a secret access point to the LHC...